Ablation catheter and method for isolating a pulmonary vein

ABSTRACT

A catheter assembly and method for treatment of cardiac arrhythmia, for example, atrial fibrillation, by electrically isolating a vessel, such as a pulmonary vein, from a chamber, such as the left atrium. The catheter assembly includes a catheter body and at least one electrode. The catheter body includes a proximal portion, an intermediate portion and a distal portion. The intermediate portion extends from the proximal portion and defines a longitudinal axis. The distal portion extends from the intermediate portion and forms a substantially closed loop transverse to the longitudinal axis. The at least one electrode is disposed along the loop. With this configuration, the loop is axially directed into contact with the chamber wall about the vessel ostium. Upon energization, the electrode ablates a continuous lesion pattern about the vessel ostium, thereby electrically isolating the vessel from the chamber.

This application is a divisional of U.S. patent application Ser. No.09/975,789, filed Oct. 11, 2001 entitled “Ablation Catheter and Methodfor Isolating a Pulmonary Vein”, now U.S. Pat. No. 6,572,612, which is adivisional of U.S. patent application Ser. No. 09/286,048, filed Apr. 5,1999, entitled “Ablation Catheter and Method for Isolating a PulmonaryVein”, now U.S. Pat. No. 6,325,797, both of which are incorporatedherein by reference in their entirety.

Cross-reference is hereby made to the following commonly assignedrelated U.S. applications filed concurrently herewith: Ser. No.10/414,800, filed Apr. 16, 2003 to Mark Stewart et al. entitled“Ablation Catheter and Method for Isolating a Pulmonary Vein” and Ser.No. 10/414,757, filed Apr. 16, 2003 to Mark Stewart entitled “AblationCatheter and Method for Isolating a Pulmonary Vein”.

BACKGROUND OF THE INVENTION

The present invention relates to an ablation catheter for treatment ofcardiac arrhythmia, for example atrial fibrillation. More particularly,it relates to an ablation catheter configured to electrically isolate avessel, such as a pulmonary vein, from a chamber, such as the leftatrium with a continuous lesion pattern and a method for forming such alesion pattern.

The heart includes a number of pathways that are responsible for thepropagation of signals necessary to produce continuous, synchronizedcontractions. Each contraction cycle begins in the right atrium where asinoatral node initiates an electrical impulse. This impulse thenspreads across the right atrium to the left atrium, stimulating theatria to contract. The chain reaction continues from the atria to theventricles by passing through a pathway known as the atrioventricular(AV) node or junction, which acts as an electrical gateway to theventricles. The AV junction delivers the signal to the ventricles whilealso slowing it, so the atria can relax before the ventricles contract.

Disturbances in the heart's electrical system may lead to variousrhythmic problems that can cause the heart to beat irregularly, too fastor too slow. Irregular heart beats, or arrhythmia, are caused byphysiological or pathological disturbances in the discharge ofelectrical impulses from the sinoatrial node, in the transmission of thesignal through the heart tissue, or spontaneous, unexpected electricalsignals generated within the heart. One type of arrhythmia istachycardia, which is an abnormal rapidity of heart action. There areseveral different forms of atrial tachycardia, including atrialfibrillation and atrial flutter. With atrial fibrillation, instead of asingle beat, numerous electrical impulses are generated by depolarizingtissue at one or more locations in the atria (or possibly otherlocations). These unexpected electrical impulses produce irregular,often rapid heartbeats in the atrial muscles and ventricles. Patientsexperiencing atrial fibrillation may suffer from fatigue, activityintolerance, dizziness and even strokes.

The precise cause of atrial fibrillation, and in particular thedepolarizing tissue causing “extra” electrical signals, is currentlyunknown. As to the location of the depolarizing tissue, it is generallyagreed that the undesired electrical impulses often originate in theleft atrial region of the heart. Recent studies have expanded upon thisgeneral understanding, suggesting that nearly 90% of these “focaltriggers” or electrical impulses are generated in one (or more) of thefour pulmonary veins (PV) extending from the left atrium. In thisregard, as the heart develops from an embryotic stage, left atriumtissue may grow or extend a short distance into one or more of the PVs.It has been postulated that this tissue may spontaneously depolarize,resulting in an unexpected electrical impulse(s) propagating into theleft atrium and along the various electrical pathways of the heart.

A variety of different atrial fibrillation treatment techniques areavailable, including drugs, surgery, implants, and catheter ablation.While drugs may be the treatment of choice for some patients, drugstypically only mask the symptoms and do not cure the underlying cause.Implantable devices, on the other hand, usually correct an arrhythmiaonly after it occurs. Surgical and catheter-based treatments, incontrast, will actually cure the problem by ablating the abnormal tissueor accessory pathway responsible for the atrial fibrillation. Thecatheter-based treatments rely on the application of various destructiveenergy sources to the target tissue, including direct current electricalenergy, radiofrequency electrical energy, laser energy, and the like.The energy source, such as an ablating electrode, is normally disposedalong a distal portion of a catheter.

Most ablation catheter techniques employed to treat atrial fibrillationfocus upon locating the ablating electrode, or a series of ablatingelectrodes, along extended target sections of the left atrium wall.Because the atrium wall, and thus the targeted site(s), is relativelytortuous, the resulting catheter design includes multiple curves, bends,extensions, etc. In response to recent studies indicating that theunexpected electrical impulses are generated within a PV, efforts havebeen made to ablate tissue within the PV itself. Obviously, the priorcatheter designs incorporating convoluted, multiple bends are notconducive to placement within a PV. Instead, a conventional “straightended” ablation catheter has been employed. While this technique oftissue ablation directly within a PV has been performed with relativelyhigh success, other concerns may arise.

More particularly, due to the relatively small thickness of atrialtissue formed within a PV, it is likely that ablation of this tissue mayin fact cause the PV to shrink or constrict. Because PV's have arelatively small diameter, a stenosis may result. Even further, othervital bodily structures are directly adjacent each PV. These structuresmay be undesirably damaged when ablating within a PV.

In light of the above, an alternative technique has been suggestedwhereby a continuous ablation lesion pattern is formed in the leftatrium wall about the ostium associated with the PV in question. Inother words, the PV is electrically isolated from the left atrium byforming an ablation lesion pattern that surrounds the PV ostium. As aresult, any undesired electrical impulse generated within the PV couldnot propagate into the left atrium, thereby eliminating unexpected atriacontraction.

Unfortunately, while PV isolation via a continuous ablation lesionpattern about the PV ostium appears highly viable, no acceptableablation catheter configuration exists. Most atrial fibrillationablation catheters have linear distal ends, designed for manipulation ina sliding fashion along the atrial wall. That is to say, the distal,electrode-carrying end of the catheter is typically slid along (orparallel to) the atrial wall. With this generally accepted configurationin mind, it may be possible to shape the distal, electrode-carrying endinto a small ring sized in accordance with the PV ostium. For example,U.S. Pat. No. 5,617,854 discloses one such possibility. Moreparticularly, the described ablation catheter includes a substantiallyring-shaped portion sized to contact the ostium of the coronary sinus.Pursuant to conventional designs, the ring extends linearly from thecatheter body. In theory, the ring-shaped portion may be placed about aPV ostium. However, proper positioning would be extremely difficult andtime consuming. More particularly, it would be virtually impossible tolocate and then align the ring about a PV ostium when sliding thecatheter along the atrium wall. The ring must be directed toward theostium in a radial direction (relative to a central axis of the ostium).Even if the electrophysiologist were able to direct the ring to theostium, the periodic blood flow through the PV would likely force thering away from the atrium wall, as the catheter body would not provideany support.

A related concern entails mapping of a PV prior to ablation. In cases ofatrial fibrillation, it is necessary to identify the origination pointof the undesired electrical impulses prior to ablation. Thus, it mustfirst be determined if the electrical impulse originates within one ormore PVs. Once the depolarizing tissue has been identified, necessaryablation steps can be taken. Mapping is normally accomplished by placingone or more mapping electrodes into contact with the tissue in question.In order to map tissue within a PV, therefore, a relatively straightcatheter section maintaining two or more mapping electrodes must beextended axially within the PV. Ablation catheters configured to slidealong the atrial wall cannot include a separate, distal extension forplacement within the PV. Instead, an entirely separate mapping cathetermust be provided and then removed for subsequent replacement with theablation catheter. Obviously, these additional steps greatly increasethe overall time required to complete the procedure.

Electrical isolation of a pulmonary vein via an ablation lesion patternsurrounding the pulmonary vein ostium presents a potentiallyrevolutionary technique for treatment of atrial fibrillation. However,the unique anatomical characteristics of a pulmonary vein and leftatrium render currently available ablation catheters minimally useful.Therefore, a substantial need exists for an ablation catheter designedfor consistent positioning of one or more ablation electrodes about apulmonary vein ostium, as well as for providing pulmonary vein mappinginformation.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a catheter assembly fortreatment of cardiac arrhythmia. The catheter assembly includes acatheter body and at least one electrode. The catheter body includes aproximal portion, an intermediate portion and a distal portion. Theintermediate portion extends from the proximal portion and defines alongitudinal axis. The distal portion extends from the intermediateportion and forms a substantially closed loop transverse to thelongitudinal axis. The electrode is disposed along the loop. With thisconfiguration, upon activation, the electrode ablates a continuouslesion pattern in a plane substantially perpendicular to thelongitudinal axis. When placed about an ostium of a vessel associatedwith a chamber formed within a patient, the continuous lesion patternestablished by the electrode electrically isolates the vessel from thechamber. For example, the catheter assembly may be provided fortreatment of atrial fibrillation whereby the lesion pattern in formed toelectrically isolate a pulmonary vein (vessel) from the left atrium(chamber). In one preferred embodiment, the catheter assembly furtherincludes a mapping device for mapping tissue within the vessel.

Another aspect of the present invention relates to a catheter assemblyfor treatment of cardiac arrhythmia. The catheter assembly comprises acatheter body and at least one electrode. The catheter body includes aproximal portion, an intermediate portion and a distal portion. Theintermediate portion extends from the proximal portion and defines alongitudinal axis. The distal portion extends from the intermediateportion and forms a substantially closed loop. The loop defines a loopaxis substantially parallel to the longitudinal axis. The electrode isdisposed along the loop. With this configuration, upon energization, theelectrode ablates a continuous lesion pattern in a plane substantiallyperpendicular to the longitudinal axis. When placed in contact withtissue, the electrode ablates a continuous lesion pattern, isolatingtissue within the lesion pattern. For example, the catheter assembly maybe provided for treatment of atrial fibrillation whereby the lesionpattern is formed to electrically isolate a pulmonary vein from the leftatrium. In one preferred embodiment, the catheter assembly furtherincludes a mapping device extending distal the loop for mapping tissue.

Another aspect of the present invention relates to a method for formingan ablation pattern to electrically isolate a vessel, defining anostium, from a chamber formed within a patient for treatment of cardiacarrhythmia. The method includes selecting a catheter assembly comprisinga catheter body and at least one electrode. The catheter body defines alongitudinal axis and includes a proximal portion and a distal portion.The distal portion forms a substantially closed loop transverse to thelongitudinal axis, the loop defining a loop axis substantially parallelto the longitudinal axis. The electrode is disposed along the loop. Thedistal portion of the catheter body is guided into the chamber and isdirected to a position spaced from the vessel ostium, with the loop axisbeing substantially aligned with a center of the vessel ostium. Thedistal portion is advanced in a direction parallel with the loop axissuch that the loop contacts the chamber wall about the vessel ostium.Finally, the electrode is energized to ablate a continuous lesionpattern about the vessel ostium to electrically isolate the vessel fromthe chamber. For example, the method may be utilized to electricallyisolate a pulmonary vein (vessel) from the left atrium (chamber) byforming a lesion pattern about the pulmonary vein ostium. In onepreferred embodiment, the method further includes mapping the vesselwith a mapping electrode.

Yet another aspect of the present invention relates to a method ofelectrically isolating a vessel from a chamber formed within a patient,the vessel defining an ostium in a wall of the chamber, for treatment ofcardiac arrhythmia. The method includes ablating a continuous, closedlesion pattern in the chamber wall about the vessel ostium. The lesionpattern electrically isolates the vessel from the chamber. For example,the method may be utilized to electrically isolate a pulmonary vein fromthe left atrium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side-elevational view of a catheter assembly in accordancewith the present invention;

FIG. 1B is a perspective view of a portion of the catheter assembly ofFIG. 1A;

FIG. 1C is an end view of a portion of the catheter assembly of FIG. 1A;

FIG. 1D is an end view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIGS. 2A-2D illustrates use of the catheter assembly of FIG. 1A within aheart;

FIG. 3A is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 3B is an end view of the catheter assembly of FIG. 3A;

FIG. 3C is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 3D is a simplified cross-sectional view of a portion of the heartand a portion of the catheter assembly of FIGS. 3A and 3B;

FIG. 4A is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 4B illustrates placement of the catheter assembly of FIG. 4A withinthe left atrium of a heart;

FIG. 5A is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 6 is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 7 is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 8 is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 9A is a side view of a portion of an alternative catheter assemblyin accordance with the present invention, in a deployed position;

FIG. 9B is a side view of the catheter assembly of FIG. 9A in aretracted position;

FIG. 10 is a side view of a portion of an alternative catheter assemblyin accordance with the present invention;

FIG. 11 is a side view of a portion of an alternative catheter assemblyin accordance with the present invention; and

FIGS. 12A and 12B are side views of a portion of an alternative catheterassembly in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One preferred embodiment of a catheter assembly 20 in accordance withthe present invention is shown in FIGS. 1A-1C. The catheter assembly 20is comprised of a catheter body 22, a handle 24 and electrodes 26. Asdescribed in greater detail below, the catheter body 22 extends from thehandle 24, and the electrodes 26 are disposed along a portion of thecatheter body 22.

The catheter body 22 is defined by a proximal portion 28, anintermediate portion 30 and a distal portion 32, and includes a centrallumen (not shown). Although not specifically shown, the catheter bodymay be configured for over-the-wire or rapid exchange applications. Inone preferred embodiment, the proximal portion 28, the intermediate 30and the distal portion 32 are integrally formed from a biocompatiblematerial having requisite strength and flexibility for deployment withina heart. Appropriate materials are well known in the art and includepolyamide.

The intermediate portion 30 extends from the proximal portion 28. Theproximal portion 28 and the intermediate portion 30 are preferablyflexible, so as to facilitate desired articulation during use. Ingeneral terms, however, the intermediate portion 30 defines alongitudinal axis L1. It should be recognized that in one position(shown in FIG. 1A), the longitudinal axis L1 extends linearly throughthe intermediate portion 30 and the proximal portion 28. Upondeployment, it may be that the proximal portion 28 and/or theintermediate portion 30 is forced to a curved or curvilinearorientation. With this in mind, the longitudinal axis L1 is morespecifically defined as a center of the intermediate portion 30 adjacenta point of intersection between the distal portion 32 and theintermediate portion 30, as best shown in FIG. 1C.

The distal portion 32 extends from the intermediate portion 30 and formsa loop 34. In one preferred embodiment, the loop 34 is circular, formedin a plane transverse to the longitudinal axis L1. To this end, thedistal portion 32 preferably includes a lateral segment 36. The lateralsegment 36 extends in a generally lateral fashion from the intermediateportion 30. The loop 34 extends from the lateral segment 36 in anarcuate fashion, turning or revolving about a central loop axis C1(shown best in FIG. 1B). While the loop 34 is shown in FIG. 1A asforming a single revolution about the central loop axis C1, the loop 34may instead include a plurality of revolutions to define a spiral orcoil. In the one preferred embodiment depicted in FIGS. 1A-1C, thecentral loop axis C1 is aligned with the longitudinal axis L1.Alternatively, however, the lateral segment 36 may be eliminated suchthat the loop 34 extends directly from the intermediate portion 30. Evenfurther, the lateral segment 36 may be configured such that the centralloop axis C1 is offset from the longitudinal axis L1. Regardless of theexact construction, however, the central loop axis C1 is preferablysubstantially parallel to the longitudinal axis L1.

As best shown in FIG. 1C, the loop 34 preferably extends to form acircle in a frontal plane. Alternatively, a variety of other shapes mayalso be useful. For example, as shown in FIG. 1D, a square-shaped loopis depicted. The loop 34 may further assume a triangular, rectangular,octagonal, or other closed shape. Returning to FIGS. 1A-1C, regardlessof the exact shape, the loop 34 is preferably substantially closed andcan be defined by a proximal end 40 and a distal end 42. To effectuatethe preferred “closed” configuration of the loop 34, the distal end 42is preferably adjacent the proximal end 40. In fact, the distal end 42may contact the proximal end 40, although this relationship is notrequired. Alternatively, the distal end 42 may be longitudinally spacedfrom the proximal end 40. With this configuration, the distal portion 32is preferably sufficiently flexible such that upon contact with a tissuewall, the distal end 42 will deflect proximally to a position adjacentthe proximal end 40.

Regardless of the exact shape, the loop 34 preferably defines anenclosed area A greater than a size of an ostium (not shown) associatedwith a particular vessel to be isolated, as described in greater detailbelow. In one preferred embodiment, the catheter assembly 20 isconfigured to electrically isolate a pulmonary vein from the leftatrium. With this one preferred application, where the loop 34 iscircular, the loop 34 has a diameter in the range of approximately 10-20mm, more preferably 15 mm, although other sizes, either greater orsmaller, are acceptable.

The loop 34 may be formed in a variety of ways, such as by incorporatinga preformed section of super elastic, shape memory material, such asNitinol, with a loop configuration. To facilitate guiding of the distalportion 32 into a heart (not shown), the catheter assembly 20 mayinclude a stylet (not shown) internally disposed within the catheterbody 22. In an extended position, the stylet would extend through thedistal portion 32, so as to render the loop 34 straight. Upon retractionof the stylet, the distal portion 32 would form the loop 34.Alternatively, the catheter assembly 20 may include a sheath (not shown)slidably receiving the catheter body 22. Prior to deployment, the distalportion 32 would be retracted within the sheath, rendering the loop 34straight. Upon deployment from the sheath, the distal portion 32 wouldform the loop 34. Other similar approaches for providing the loop 34 aresimilarly acceptable.

The handle 24 is preferably sized to be grasped by a user and includesan electrical connector 44. The electrical connector provides electricalconnections to the electrodes 26 carried by the distal portion 32. Tothis end, wire(s) (not shown) may extend within the central lumen (notshown) from the distal portion 32 to the handle 24.

The electrodes 26 are preferably of a type known in the art and arepreferably a series of separate band electrodes spaced along the loop34. Instead of, or in addition to, separate band electrodes, theelectrodes 26 may include one or more spiral or coil electrodes, or oneor more counter-electrodes. Additionally, the electrodes 26 arepreferably non-thrombogenic, non-coagulum or char forming. Theelectrodes 26 may be cooled by a separate source (not shown), such as asaline source. The electrodes 26 may be electrically isolated from oneanother, or some or all of the electrodes 26 may be electricallyconnected to one another. Preferably, however, at least one electrode 26is provided. The electrodes 26 are preferably shaped and positioned suchthat during an ablation procedure, a continuous, closedtherapeutically-effective lesion pattern is created. Preferably, thelength of each of the electrodes 26 is about 4-12 mm, more preferablyabout 7 mm. The spacing between each of the electrodes 26 is preferablyabout 1-3 mm, and more preferably about 2 mm. Finally, to effectuate acontinuous, closed lesion pattern, preferably one of the electrodes 26is disposed at the proximal end 40 of the loop 34, and another of theelectrodes 26 is disposed at the distal end 42. As previously described,it is not necessary that the loop segment 38 be formed such that theproximal end 40 and the distal end 42 are integral. Instead, a slightspacing may exist. With this in mind, the spacing or gap between theelectrode 26 at the proximal 40 and the electrode 26 at the distal end42 is preferably less than about 5 mm.

FIGS. 2A and 2B illustrate use of the catheter assembly 20 shown inFIGS. 1A-1C within a heart 50. As a point of reference, the heart 50includes a right atrium RA, a left atrium LA, a right ventricle RV and aleft ventricle LV. An inferior vena cava IVC and a superior vena cavaSVC lead into the right atrium RA. The right atrium RA is separated fromthe left atrium LA by an interarterial septum (not shown). Finally, fourpulmonary veins PV extend from the left atrium LA. Each of the pulmonaryveins PV forms an ostium PVO in the left atrium LA wall. As previouslydescribed, during formation of the heart 50, it is possible that tissueof the left atrium LA may grow upwardly into one or more of thepulmonary veins PV. This left atrium LA tissue may spontaneouslydepolarize, resulting in atrial fibrillation. Notably, the heart 50 maybe formed such that a separate ostium PVO is not formed for eachindividual pulmonary vein PV. In other words, a single pulmonary veinostium PVO may be formed for two pulmonary veins PV. For example, asingle pulmonary vein ostium PVO may be formed for both the leftinferior pulmonary vein PV and the left superior pulmonary vein PV, withthe two pulmonary veins PV bifurcating from the single ostium PVO.

As shown in FIG. 2A, electrical isolation of a pulmonary vein PV beginsby directing the distal portion 32 of the catheter body 22 through theinferior vena cava IVC, into the right atrium RA through a puncture inthe interarterial septum (not shown) and into the left atrium LA.Alternatively, the introduction of the distal portion 32 of the catheterbody 22 into the right atrium RA is also suggested by passage of thedistal portion 32 into the right atrium RA through the superior venacava SVC. The loop 34 is positioned slightly spaced from the ostium PVOassociated with the pulmonary vein PV to be treated. More particularly,the loop 34 is positioned such that the central loop axis C1 (FIG. 1B)is approximately aligned with a center of the pulmonary vein ostium PVO.The catheter body 22 is then advanced distally such that the loop 34contacts the left atrium LA wall about the pulmonary vein ostium PVO inquestion, as shown in FIG. 2B. In other words, the catheter body 22 isadvanced in a direction parallel with the central loop axis C1 such thatthe loop 34 contacts the left atrium LA wall, surrounding the pulmonaryvein ostium PVO. Importantly, because the central loop axis C1 isparallel to the longitudinal axis L1, the catheter body 22longitudinally supports advancement of the loop 34. In other words, thelongitudinal axis L1 is effectively aligned with the pulmonary veinostium PVO such that blood flow from the pulmonary vein PV acts alongthe longitudinal axis L1. Thus, the catheter body 22 limits deflectionof the loop 34 otherwise caused by blood flow from the pulmonary veinPV.

The electrodes 26 (shown best in FIGS. 1A-1C) are then energized to asufficient level to ablate the contacted tissue, for example with anr.f. source. In one preferred embodiment, the electrodes 26 ablate theleft atrium LA tissue for 30-120 seconds at a temperature in the rangeof approximately 60-70 degree C. As a result, a continuous, closedlesion pattern is formed around the pulmonary vein ostium PVO as shownin FIG. 2C. Pursuant to the above described catheter assembly 20configuration, the lesion pattern is formed in a plane substantiallyperpendicular to the longitudinal axis L1. Notably, while the lesionpattern is shown as being only slightly larger than the pulmonary veinostium PVO, the loop 34 (FIG. 1A) may be sized to produce an even largerablation lesion pattern. To this end, where a single pulmonary veinostium PVO is formed for two pulmonary veins PV, the resulting pulmonaryvein ostium PVO may be elongated. As shown in FIG. 2D, then, the loop 34(FIG. 1A) is configured to form a continuous, closed lesion patternabout the elongated-shaped pulmonary vein ostium PVO.

The continuous, closed lesion pattern electrically isolates thepulmonary vein PV from the left atrium LA. Any undesired electricalimpulses generated in the pulmonary vein are effectively “stopped” atthe lesion pattern, and will not propagate into the left atrium LA.

An alternative catheter assembly 60 is shown in FIGS. 3A and 3B. Thecatheter assembly 60 includes a catheter body 62, a handle (not shown)and electrodes 64. The catheter body 62 includes a proximal portion (notshown), an intermediate portion 66 and a distal portion 68. For ease ofillustration, the handle and the proximal portion of the catheter body22 are not shown in FIGS. 3A and 3B, it being understood that thesecomponents are similar to the handle 24 and the proximal portion 28shown in FIG. 1A. Similar to the catheter body 22, the intermediateportion 66 extends from the proximal portion and defines a longitudinalaxis L2. The distal portion 68 extends from the intermediate portion 66and forms a loop or coil 70 substantially transverse to the longitudinalaxis L2 and includes a plurality of loop segments 72A-72C. The coil 70is formed such that each of the loop segments 72A-72C revolves about acentral loop axis C2. In one preferred embodiment, the central loop axisC2 is aligned with the longitudinal axis L2 defined by the intermediateportion 66. Alternatively, the central loop axis C2 may be offset fromthe longitudinal axis L2. Regardless, the central loop axis C2 ispreferably substantially parallel with the longitudinal axis L2.

Each of the loop segments 72A-72C preferably defines a differentdiameter. For example, the first loop segment 72A defines a diameterslightly larger than that of the second loop segment 72B; whereas thesecond loop segment 72B defines a diameter slightly greater than that ofthe third loop segment 72C. In this regard, while each of the loopsegments 72A-72C are depicted as being longitudinally spaced (such thatthe loop 70 forms a multi-lane spiral or coil), the loop segments72A-72C may instead be formed in a single plane (such that the loop 70forms a unitary plane spiral or coil). While the loop segments 72A-72Cextend distal the intermediate portion 66 so as to define a descendingor decreasing diameter, an opposite configuration may also be employed.For example, FIG. 3C depicts a coil 70′ having loop segments distallyincreasing in diameter.

Returning to FIGS. 3A and 3B, the electrodes 64 are similar to theelectrodes 26 (FIG. 1A) previously described, and preferably are bandelectrodes disposed along the loop segments 72A-72C. In this regard,each of the loop segments 72A-72C includes electrodes 64A-64C,respectively. In one preferred embodiment, a power source (not shown)associated with the electrodes 64 is configured to individually energizethe electrodes 64 to varying levels. Further, the electrodes 64 arepreferably configured to provide feedback information indicative oftissue contact, such as by including a thermocouple.

The catheter assembly 60 is used in a fashion highly similar to themethod previously described for the catheter assembly 20 (as shown, forexample, in FIGS. 2A-2C). Thus, for example, the distal portion 68 ofthe catheter body 62 is directed within the left atrium LA (FIG. 2A)such that the loop 70 is disposed about a pulmonary vein ostium PVO. Itshould be understood that one or more of the loop segments 72A-72C maydefine a diameter (or area) that is less than a diameter (or area) ofthe pulmonary vein ostium PVO in question. For example, in thesimplified cross-sectional view of FIG. 3D, the electrodes 64Cassociated with the third loop segment 72C (FIG. 3A) are not in contactwith the left atrium LA wall, but instead are within the area defined bythe pulmonary vein ostium PVO. Conversely, the electrodes 64B associatedwith the second loop segment 72B (FIG. 3A) and the electrodes 64Aassociated with the first loop segment (FIG. 3A) are in contact with theleft atrium LA wall. To avoid potential collateral damage caused by fullenergization of the electrodes 64C not in contact with the left atriumLA wall, each of the electrodes 64A-64C are selectively energized with alow energy supply. The energy level is not sufficient to ablatecontacted tissue, but provides a low energy measurement, such as througha thermocouple or other sensing device associated with each of theelectrodes 64A-64C. If the sensing device detects a temperature rise, anindication is given that the particular energized electrode 64A, 64B or64C is in contact with tissue of the left atrium LA. Following the lowenergy measurement procedure, only those electrodes determined to be incontact with the left atrium LA (for example, electrodes 64A and 64B)are powered to ablate a continuous, closed lesion pattern about thepulmonary vein ostium PVO, as previously described.

Another alternative embodiment of a catheter assembly 80 is shown inFIG. 4A. The catheter assembly 80 includes a catheter body 82, anelectrode 84 and a locating device 86. For ease of illustration, only aportion of the catheter assembly 80 is shown, and catheter assembly 80may further include a handle similar to the handle 24 associated withthe catheter assembly 20 (FIG. 1A) previously described.

Catheter body 82 is defined by a proximal portion (not shown), anintermediate portion 88 and a distal portion 90. The intermediateportion 88 extends from the proximal portion and is defined by aproximal segment 92 and a distal segment 94. In a preferred embodiment,the distal segment 94 is preferably more flexible than the proximalsegment 92. With this configuration, the distal segment 94 can moreeasily deflect relative to the proximal segment 92, thereby facilitatingdesired positioning of the distal portion 90 during deployment. In thisregard, an internal pull wire (not shown) may be provided to effectuatedesired deflection of the distal segment 94. Even further, an anchor 96is preferably included for facilitating a more radical displacement ofthe distal portion 90 relative to the intermediate portion 88.

As with previous embodiments, the intermediate portion 88 defines alongitudinal axis L3. Once again, where the intermediate portion 88 isaxially aligned with the proximal portion (not shown), the longitudinalaxis L3 is linear along the intermediate portion 88 and the proximalportion. However, because the intermediate portion 88 is preferablybendable relative to the proximal portion, and further because thedistal segment 94 may bend relative to the proximal segment 92, thelongitudinal axis L3 is more succinctly defined by the intermediateportion 88 at the point of intersection between the intermediate portion88 and the distal portion 90.

Similar to the catheter assembly 20 (FIG. 1A) previously described, thedistal portion 90 preferably forms a loop 98. The loop 98 may includeone or more loop segments (one is shown in FIG. 4A), with each loopsegment revolving around a central loop axis C3. The loop 98 is formedsubstantially transverse to the longitudinal axis L3, with the centralloop axis C3 preferably aligned with the longitudinal axis L3.Alternatively, the central loop axis C3 may be slightly offset from thelongitudinal axis L3. Regardless, the central loop axis C3 is preferablyparallel with the longitudinal axis L3.

The electrode 84 is shown in FIG. 4 as being a continuous coilelectrode. Alternatively, a plurality of spaced, band electrodes orcounter-electrodes may be used.

Finally, the locating device 86 includes a tip 104 configured to extenddistal the loop 98. In one preferred embodiment, the locating device 86is integrally formed with the catheter body 82, extending from thedistal portion 90. Alternatively, the locating device 86 may be aseparate body. Regardless, the tip 104 extends distal the distal portion90, and is aligned with the central loop axis C3 defined by the loop 98.The tip 104 preferably has a diameter less than a diameter of apulmonary vein, and a length in the range of approximately 1-15 mm.Further, as shown in FIG. 4, the tip 104 may include a series of mappingelectrodes 102. The mapping electrodes 102 are electrically connected toan external recording system (not shown) for providing informationindicative of tissue polarization.

As shown in FIG. 4B, during use, the catheter assembly 80 is directedinto the left atrium LA as previously described. The locating device 86,and in particular the tip 104, is then used to locate the pulmonary veinostium PVO. Once located, the tip 104 is inserted into the pulmonaryvein PV, effectively centering the loop 98 around the pulmonary veinostium PVO. Where the tip 104 includes the mapping electrodes 102, amapping procedure can be performed, whereby information indicative oftissue activity nearby the mapping electrodes 102 is provided. Duringthis mapping procedure, a determination can be made as to whether theparticular pulmonary vein PV is generating undesired electricalimpulses. Where it is determined that, in fact, tissue in the pulmonaryvein PV is spontaneously depolarizing, the electrode 84 is energized toform the continuous, closed lesion pattern about the pulmonary veinostium PVO as previously described.

Yet another alternative embodiment of a catheter assembly 110 inaccordance with the present invention is shown in FIG. 5. The catheterassembly 110 is highly similar to the catheter assembly 80 (FIG. 4A) andincludes a catheter body 112, electrodes 114 and a locating device 116.The catheter body 112 includes a proximal portion (not shown) anintermediate portion 88 defining a longitudinal axis L4 and a distalportion 120. The distal portion 120 extends from the intermediateportion 118 and forms a loop 122 substantially transverse to thelongitudinal axis L4. In this regard, the loop 122 revolves about acentral loop axis C4. In one preferred embodiment, the central loop axisC4 is aligned with the longitudinal axis L4. Alternatively, the centralloop axis C4 is offset from, but substantially parallel with, thelongitudinal axis L4. The electrodes 114 (shown as spaced bandelectrodes) are disposed along the loop 122 for forming a continuos,closed lesion pattern.

The locating device 116 includes a tip 124 that extends distal the loop122. In one preferred embodiment, the locating device 116 is integrallyformed with the catheter body 112 and includes mapping electrodes 126connected to an external recording device (not shown). Alternatively,the locating device 116 may be a separate body. As shown in FIG. 5, thetip 124 forms a descending diameter coil, generally aligned with thecentral loop axis C4. By providing a coil configuration for the tip 124,the tip 124 facilitates a more positive centering of the loop 122 abouta pulmonary vein ostium PVO (FIG. 4B). In one preferred embodiment, thetip 124 defines a maximum diameter approximating a diameter of apulmonary vein. When inserted within a pulmonary vein, then, the tip 124effectively lodges along the pulmonary vein wall. This, in turn,positions the loop 122 in a more central fashion about the associatedostium. Further, by providing the mapping electrodes 126, the locatingdevice 116 additionally serves as a mapping device for evaluating aparticular pulmonary vein.

It should be recognized that other devices can be provided to assist incentering the ablation loop about the pulmonary vein ostium. Forexample, yet another alternative embodiment of a catheter assembly 130is depicted in FIG. 6. The catheter assembly includes a catheter body132, electrodes 134, a balloon 136 and a locating device 138. Thecatheter body 132 is similar to those previously described, and includesa proximal portion (not shown) an intermediate portion 140 defining alongitudinal axis L5 and a distal portion 142. The distal portion 142extends from the intermediate portion 140 and forms a loop 144substantially transverse to the longitudinal axis L5. The loop 144revolves about a central loop axis C5, that, in one preferredembodiment, is aligned with the longitudinal axis L5. The balloon 136 isdisposed along the distal portion 142 distal the loop 144. In onepreferred embodiment, the balloon 136 is fluidly connected to a fluidsource (not shown), such as a pressurized reservoir of saline, by alumen (not shown) formed within the catheter body 132. Finally, thelocating device 138 includes a tip 146 extending distal the loop 144. Inone preferred embodiment, as shown in FIG. 6, the locating device 138 isintegrally formed with the catheter body 132, with the tip 146 extendingdistal the balloon 136. Alternatively, the locating device 138 may be aseparate body, and the tip 146 may be positioned between the loop 144and the balloon 136. Regardless, the tip 146 preferably includes mappingelectrodes 148.

During use, the locating device 138 is used to locate a pulmonary veinPV (FIG. 4B) via the tip 146. The tip 146 axially inserted into thepulmonary vein PV. The mapping electrodes 148 may then be used toascertain whether tissue in the pulmonary vein PV is spontaneouslygenerating unexpected electrical impulses. Upon determining that thepulmonary vein PV requires electrical isolation, the catheter body 132is deployed such that the loop 144 contacts the left atrium LA (FIG. 4B)wall (as previously described). The balloon 136 is inflated such that itengages the pulmonary vein PV wall. Once inflated, the balloon 136positively centers the loop 144 about the pulmonary vein ostium PVO(FIG. 4B).

Yet another alternative embodiment of a catheter assembly 160 is shownin FIG. 7. The catheter assembly 160 includes a catheter body 162,electrodes 164, a wire basket 166 and a locating device 168. As withprevious embodiments, the catheter body 162 includes a proximal portion(not shown), an intermediate portion 170 defining a longitudinal axis L6and a distal portion 172. The distal portion 172 extends from theintermediate portion 170 and forms a loop 174 transverse to thelongitudinal axis L6. In this regard, the loop 174 revolves around acentral loop axis C6 that, in one preferred embodiment, is aligned withthe longitudinal axis L6.

The wire basket 166 is maintained by the distal portion 172 distal theloop 174. The wire basket 166 may be radially extended and retracted viaa pull wire or similar activation device extending through a lumen (notshown) formed within the catheter body 162.

Finally, the locating device 168 includes a tip 176 positioned distalthe loop 174. In one preferred embodiment, the locating device 168 isintegrally formed with the catheter body 162 and includes mappingelectrodes 178. Alternatively, the locating device 168 may be a separatebody, and the tip 176 may be disposed between the wire basket 166 andthe loop 174.

During use, the catheter assembly 160 functions in a fashion highlysimilar to the catheter assembly 130 (FIG. 6) previously described. Thelocating device 168, and in particular the tip 176, is used to locateand map a pulmonary vein PV (FIG. 4B). The loop 174 is maneuvered intocontact with the left atrium LA (FIG. 4B) wall. The wire basket 166 isthen radially deployed so as to engage the pulmonary vein PV wall. Inthis deployed position, the wire basket 166 serves to positively centerthe loop 174 about the pulmonary vein ostium PVO (FIG. 4B).

Yet another alternative embodiment of a catheter assembly 190 is shownin FIG. 8. The catheter assembly 190 includes a catheter body 192 (shownpartially in FIG. 8), electrodes 194, a locating device 196 and a guidecatheter or sheath 198. As described in greater detail below, the sheath198 coaxially maintains the catheter body 192 and the locating device196 such that each of the catheter body 192 and the locating device 196are slidable between a retracted position and a deployed position (shownin FIG. 8).

The catheter body 192 is virtually identical to the catheter body 62(FIG. 3A) previously described and includes a proximal portion (notshown), an intermediate portion 200 defining a longitudinal axis L7 anda distal portion 202. The distal portion 202 extends from theintermediate portion 200 and forms a coil or plurality of loops 204substantially transverse to the longitudinal axis L7. Alternatively, thecoil 204 may form a single loop. The coil 204 revolves around a centralloop axis C7, that, in one preferred embodiment, is aligned with thelongitudinal axis L7. The distal portion 202, and in particular the coil204, is preferably sufficiently flexible so as to assume a relativelystraight configuration when retracted within the sheath 198. Further,the distal portion 202 includes a shape memory characteristic such thatwhen deployed from the sheath 198, the distal portion 202 forms the coil204 as shown in FIG. 8.

The electrodes 194 are identical to those previously described andpreferably comprise band electrodes disposed along the coil 204.Alternatively, a continuous coil electrode or counter-electrode may beprovided.

The locating device 196 is relatively rigid and includes a shaft 206defining a tip 208 that preferably maintains mapping electrodes 210. Theshaft 206 is sized to be slidably received within a lumen (not shown) inthe sheath 198. As shown in FIG. 8, the tip 208 preferably assumes acoil shape with decreasing diameter. Alternatively, the tip 208 may besubstantially straight. Preferably, however, the tip 208 is sufficientlyflexible such that upon retraction into the sheath 198, the tip 208assumes a relatively straight form. Additionally, the tip 208 has ashape memory characteristic such that upon deployment from the sheath198, the tip 208 assumes the coiled shape shown in FIG. 8. For example,the tip 208 may include stainless steel or Nitinol core wires. Further,the tip 208 may be formed from a shape memory alloy of Nitinol thatforms the coil shape when heated above a certain temperature. The heatmay be achieved through resistive heating of the wire directly, or bysurrounding the wire with a tubular heater.

The sheath 198 includes a proximal end (not shown) and a distal end 212,and forms at least one central lumen (not shown) sized to maintain thecatheter body 192 and the locating device 196. Alternatively, a separatelumen may be provided for each of the catheter body 192 and the locatingdevice 196. Regardless, the sheath 198 is configured to slidablymaintain each of the catheter body 192 and the locating device 196 in arelatively close relationship. In one preferred embodiment, the sheath198 is formed of a relatively soft material such as 35D or 40D Pebex.

As described above, each of the catheter body 192 and the locatingdevice 196 are slidable relative to the sheath 198. In a deployedposition (depicted in FIG. 8), the distal portion 202 of the catheterbody 192 and the tip 208 of the locating device 196 extend distally fromthe sheath 198. More particularly, the locating device 196 is positionedsuch that the tip 208 is distal the coil 204. In this extended position,the tip 208 is essentially aligned with the central loop axis L7.

During use, the catheter body 192 and the locating device 196 areretracted within the sheath 198. The sheath 198 is then guided to theleft atrium LA (FIG. 4B). The catheter body 192 and the locating device196 are deployed from the sheath 198. More particularly, the distalportion 202 of the catheter body 192 and the tip 208 of the locatingdevice 196 are extended from the distal end 212 of the sheath 198 (asshown in FIG. 8). A locking device (not shown) is preferably provided tosecure the catheter assembly 190 in the deployed position. As previouslydescribed, upon deployment, the distal portion 202 forms the coil 204,whereas the tip 208 preferably assumes a coil shape. The tip 208 locatesand is directed axially into a pulmonary vein PV as previouslydescribed. The mapping electrodes 210 sample electrical activity of thepulmonary vein tissue. If the mapping procedure determines that thepulmonary vein PV requires electrical isolation, the sheath 198 isguided in a direction along the central loop axis C7 until the coil 204contacts the left atrium LA (FIG. 4B) wall about the pulmonary veinostium PVO (FIG. 4B). Because the catheter body 192 and the locatingdevice 196 are directly connected by the sheath 198, the tip 208effectively positively centers the loop 204 about the pulmonary veinostium PVO. The electrodes 194 may be selectively energized with a lowenergy supply to determine which of the electrodes 194 are in contactwith tissue of the left atrium LA. Some or all of the electrodes 194 arethen energized to ablate a continuous, closed lesion pattern about thepulmonary vein ostium PVO, thereby electrically isolating the pulmonaryvein PV from the left atrium LA.

While the catheter assembly 190 has been described as including thesheath 198 to maintain the catheter body 192 and the locating device196, the sheath 198 may be eliminated for example, the catheter body 192may alternatively be configured to include lumen (not shown) sized toslidably receive the locating device 192. In this regard, the locatingdevice 192 may serve as a guide wire, with the catheter body 192 ridingover the locating device 192 much like an over-the-wire catheterconfiguration commonly known in the art. Even further, the catheter body192 may include a rapid exchange design characteristic for quickmounting to removal from the locating device 190.

Yet another alternative embodiment of a catheter assembly 220 is shownin FIGS. 9A and 9B. The catheter assembly 220 includes a catheter body222 (shown partially in FIGS. 9A and 9B), electrodes 224, stylets 226and a locating device 228. The electrodes 224 are disposed along aportion of the catheter body 222. The stylets 226 are slidablymaintained within the catheter body 222. Finally, the locating device228 is slidably maintained by the catheter body 222.

The catheter body 222 is similar to those previously described andincludes a proximal portion (not shown), an intermediate portion 230,defining a longitudinal axis L8, and a distal portion 232. The distalportion 232 forms a loop 234 substantially transverse to thelongitudinal axis L8. The loop 234 revolves around a central loop axisC8 which, in one preferred embodiment, is aligned with the longitudinalaxis L8. The distal portion 232 is preferably sufficiently flexible soas to be relatively straight in a retracted position (FIG. 9B). Further,the distal portion 232 has a shape memory characteristic such that thedistal portion 232 forms the loop 234 in a deployed position (FIG. 9A).For example, the catheter body 222 may be formed of a super elastic,shape memory Nitinol alloy.

Each of the stylets 226 are relatively rigid shafts sized to be slidablyreceived within lumens (not shown) formed by the catheter body 222. Tothis end, as shown in FIG. 9A, in a deployed position, the stylets 226are proximal the distal portion 232 such that the distal portion 232 isallowed to form the loop 234. Conversely, in a retracted position (FIG.9B) the stylets 226 extend into the distal portion 232, therebyrendering the distal portion 232 substantially straight.

The electrodes 224 are identical to those previously described andpreferably comprise band electrodes disposed along the loop 234.Alternatively, a continuous coil electrode or counter electrode may beprovided.

The locating device 228 includes a shaft 236 having a tip 238. Similarto previous embodiments, the tip 238 is preferably coil shaped, andincludes mapping electrodes 240. In this regard, the tip 238 ispreferably sufficiently flexible such that in the retracted position(FIG. 9B), the tip 238 is rendered relatively straight by the catheterbody 222. Conversely, in the deployed position (FIG. 9A), the tip 238assumes the coiled shape. Alternatively, the tip 238 may besubstantially straight in the deployed position.

The catheter assembly 220 is used in a manner highly similar to thatpreviously described. The catheter assembly 220 is initially placed inthe retracted position (FIG. 9B), whereby the stylets 226 are maneuvereddistally to straighten the distal portion 232. Further, the locatingdevice 228 is retracted within the catheter body 222 such that tip 238is proximal the distal portion 232 and is rendered relatively straight.In this retracted position, the catheter assembly 222 can more easily bedirected into the left atrium LA (FIG. 4B) as previously described. Oncein the left atrium LA, the catheter assembly 220 is maneuvered to thedeployed position (FIG. 9A), whereby the stylets are moved proximallysuch that the distal portion 232 forms the loop 234. Further, thelocating device 228 is maneuvered distally relative to the catheter body222 such that the tip 238 extends distal the loop 234. In the deployedposition, the locating device 228 is maneuvered in a generally axialfashion to locate and extend into a pulmonary vein PV. The mappingelectrodes 240 map the pulmonary vein tissue (FIG. 4B). Where themapping procedure indicates that the pulmonary vein PV requireselectrical isolation, the catheter assembly 220 is advanced such thatthe loop 234 surrounds the pulmonary vein ostium PVO (FIG. 4B). Moreparticularly, the catheter assembly 220 is advanced in the direction ofthe central loop axis C8. Once again, the unique configuration of thecatheter assembly 220 facilitates movement in an axial direction(relative to the pulmonary vein ostium PVO) as opposed to a radial,sliding direction required by previous ablation catheter designs.Notably, because the locating device 228 is directly connected to thecatheter body 222, the locating device 228 facilitates positivecentering of the loop 234 about the pulmonary vein ostium PVO. Theelectrodes 224 are then energized to ablate a continuous, closed lesionpattern about the pulmonary vein ostium PVO, thereby electricallyisolating the pulmonary vein PV.

Yet another alternative embodiment of the catheter assembly 250 inaccordance with the present invention is shown in FIG. 10. The catheterassembly 250 includes a catheter body 252 (shown partially in FIG. 10),electrodes 254, a locating device 256 and a guide catheter or sheath258. As described in greater detail below, the sheath 258 coaxiallymaintains the catheter body 252 and the locating device 256 such thateach of the catheter body 252 and the locating device 256 are slidablebetween a retracted position and a deployed position (shown in FIG. 10).

The catheter body 252 is virtually identical to the catheter body 62(FIG. 3A) previously described and includes a proximal portion (notshown), an intermediate portion 260 defining a longitudinal axis L9 anda distal portion 262. The distal portion 262 extends from theintermediate portion 260 and forms a coil or loops 264 substantiallytransverse to the longitudinal axis L9. Alternatively, the coil 264 mayform a single loop. The coil 264 revolves around a central loop axis C9,that, in one preferred embodiment, is aligned with the longitudinal axisL9. The distal portion 262, and in particular the coil 264, ispreferably sufficiently flexible so as to assume a relatively straightconfiguration when retracted within the sheath 258. Further, the distalportion 262 includes a shape memory characteristic such that whendeployed from the sheath 258, the distal portion 262 forms the coil 264as shown in FIG. 10.

The electrodes 254 are identical to those previously described andpreferably comprise band electrodes disposed along the coil 264.Alternatively, a continuous coil electrode or counter-electrode may beprovided.

The locating device 256 includes a shaft 266 and a balloon 268. Theshaft 266 includes a distal portion 270 and a tip 272. The distalportion 270 preferably forms an expansion joint 274. The tip 272 isdistal the expansion joint 274 and preferably maintains mappingelectrodes 276. The balloon 268 is sealed to the distal portion 270 ofthe shaft 266 about the expansion joint 274. In this regard, theexpansion joint 274 is configured to be manipulated between a contractedposition (FIG. 10) and an expanded position. In the expanded position,the expansion joint 274 extends axially so as to collapse the balloon268. When collapsed, the balloon 268 can more easily be retracted withinthe sheath 258.

The sheath 258 includes a proximal end (not shown) and a distal end 278,and forms at least one central lumen (not shown) sized to maintain thecatheter body 252 and the locating device 256. Alternatively, a separatelumen may be provided for each of the catheter body 252 and the locatingdevice 256. Regardless, the sheath 258 is configured to slidablymaintain each of the catheter body 252 and the locating device 256 inrelatively close relationship. In one preferred embodiment, the sheath258 is formed of a relatively soft material such as 35D or 40D Pebex.

As described above, each of the catheter body 252 and the locatingdevice 256 are slidable relative to the sheath 258. In a deployedposition (depicted in FIG. 10), the distal portion 262 of the catheterbody 252 and the distal portion 270 of the locating device 256 extenddistally from the sheath 258. More particularly, the coil 264 ispositioned distal the distal end 278 of the sheath 258. Further, thedistal portion 270, including the balloon 268, of the locating device256 is positioned distal the coil 264. In this position, the distalportion 270 is essentially aligned with the central loop axis L9.

Prior to use, the catheter body 252 and the locating device 256 areretracted within the sheath 258. The sheath 258 is then guided to theleft atrium LA (FIG. 4B). The catheter body 252 and the locating device256 are deployed from the sheath 258. More particularly, the distalportion 262 of the catheter body 252 and the distal portion 270 of thelocating device 256 are extended from the distal end 278 of the sheath258 (as shown in FIG. 10). A locking device (not shown) is preferablyprovided to secure the catheter assembly 250 in the deployed position.As previously described, upon deployment, the distal portion 262 of thecatheter body 252 forms the coil 264. The distal portion 270 of thelocating device 256, including the balloon 268, is positioned distal thecoil 264. The tip 272 locates and is directed axially into a pulmonaryvein PV (FIG. 4B) as previously described. The mapping electrodes 276sample electrical activity of the pulmonary vein tissue. If the mappingprocedure determines that the pulmonary vein PV requires electricalisolation, the sheath 258 is guided in a direction along the centralloop axis C9 until the coil 264 contacts the left atrium LA wall aboutthe pulmonary vein ostium PVO (FIG. 4B). The expansion joint 274 iscontracted and the balloon 268 inflated. Once inflated, the balloon 268engages the pulmonary vein PV. Because the catheter body 252 and thelocating device 256 are directly connected by the sheath 258, theballoon 268 effectively positively centers the coil 264 about thepulmonary vein ostium PVO. The electrodes 254 may be selectivelyenergized with a low-energy supply to determine which of the electrodes254 are in contact with the tissue of the left atrium LA. Some or all ofthe electrodes 254 are then energized to ablate a continuous, closedlesion pattern about the pulmonary vein ostium PVO, thereby electricallyisolating the pulmonary vein PV from the left atrium LA.

Yet another alternative embodiment of a catheter assembly 290 is shownin FIG. 11. The catheter assembly 290 is highly similar to the catheterassembly 250 (FIG. 10) previously described, and includes a catheterbody 292, electrodes 294, a locating device 296 and a guide catheter orsheath 298. The sheath 298 coaxially maintains the catheter body 292 andthe locating device 296 such that each of the catheter body 292 and thelocating device 296 are slidable between a retracted position and adeployed position (shown in FIG. 11).

The catheter body 292 includes a proximal portion (not shown), anintermediate portion 300 defining a longitudinal axis L10 and a distalportion 302. The distal portion 302 extends from the intermediateportion 300 and forms a coil or plurality of loops 304 substantiallytransverse to the longitudinal axis L10. Alternatively, the coil 304 mayform a single loop. The coil 304 revolves around a central loop axisL10, that, in one preferred embodiment, is aligned with the longitudinalaxis L10. The distal portion 302, and in particular the coil 304, ispreferably sufficiently flexible so as to assume a relatively straightconfiguration when retracted within the sheath 298. Further, the distalportion 302 includes a shape memory characteristic such that whendeployed from the sheath 298, the distal portion 302 forms the coil 304as shown in FIG. 11.

The electrodes 294 are identical to those previously described andpreferably comprise band electrodes disposed along the coil 304.Alternatively, a continuous coil electrode or counter-electrode may beprovided.

The locating device 296 includes a shaft 306 and a wire basket 308. Theshaft 306 includes a distal portion 310 and a tip 312. The distalportion 310 forms an expansion joint 314. The tip 312 preferablymaintains mapping electrodes 316. The wire basket 308 is secured to thedistal portion 310 about the expansion joint 314. With thisconfiguration, the expansion joint 314 can be manipulated between anexpanded position in which the wire basket 308 is relatively flat and acontracted position (FIG. 11) in which the wire basket 308 expandsradially.

The sheath 298 is highly similar to previous embodiments and includes aproximal end (not shown) and a distal end 318, and forms at least onecentral lumen (not shown) sized to maintain the catheter body 292 andthe locating device 296. Alternatively, a separate lumen may be providedfor each of the catheter body 292 and the locating device 296.Regardless, the sheath 298 is configured to slidably maintain each ofthe catheter body 292 and the locating device 296 in a relatively closerelationship.

As described above, each of the catheter body 292 and the locatingdevice 296 are slidable relative to the sheath 298. In a deployedposition (depicted in FIG. 11), the distal portion 302 of the catheterbody 292 and the distal portion 310 of the locating device 296 extenddistally from the sheath 298. More particularly, the catheter body 292is positioned such that the coil 304 is distal the distal end 318.Further, the distal portion 310 of the locating device 296 is distal thecoil 304.

During use, the catheter assembly 290 functions in a manner highlysimilar to the catheter assembly 250 (FIG. 10) previously described.However, the wire basket 308 is used to positively center the coil 304about a pulmonary vein ostium PVO instead of the balloon 268 (FIG. 10)previously described.

Yet another alternative embodiment of the catheter assembly 330 is shownin FIGS. 12A and 12B. The catheter assembly 330 includes a catheter body332 (shown partially in FIGS. 12A and 12B), a wire basket 334, alocating device 336 and a stylet or guide wire 338. The wire basket 334is secured to the catheter body 332. The locating device 336 ispreferably integrally formed with the catheter body 332 and includes aballoon 340. Finally, the guide wire 338 is slidably disposed within acentral lumen (not shown) in the catheter body 332 and the locatingdevice 336.

The catheter body 332 includes a proximal portion (not shown), anintermediate 342 defining a longitudinal axis L11 and a distal portion344. The distal portion 344 maintains a proximal collar 346 and a distalcollar 348. In a preferred embodiment, the proximal collar 346 isslidable relative to the distal collar 348.

The wire basket 334 is secured to the distal portion 344 by the proximalcollar 346 and the distal collar 348. Further, the wire basket 334includes a plurality of individual wire struts 350 each maintaining anelectrode 352. In a preferred embodiment, the wire struts 350 arepreferably tubular and are fluidly connected to a cooling source. Theelectrodes 352 are preferably disposed along the wire struts 350,respectively, slightly distal of a central position. With thisconfiguration, the wire basket 334 can be maneuvered between a retractedposition (FIG. 12A) and an expanded position (FIG. 12B) with movement ofthe proximal collar 346 relative to the distal collar 348. Notably, inthe expanded position of FIG. 12B, the wire basket 334 positions theelectrodes 352 so as to form a loop transverse to the longitudinal axisL11. More particularly, the loop formed in the expanded positionrevolves around a central loop axis C11, that, in one preferredembodiment, is aligned with the longitudinal axis L11.

The electrodes 352 are identical to those previously described andpreferably comprise band electrodes disposed along the wire basket 334.

The locating device 336 extends distal the distal collar 348, andmaintains the balloon 340 and mapping electrodes 354. The balloon 340 isfluidly connected to an inflation source (not shown) by a lumen (notshown) formed within the catheter body 332. As shown in FIGS. 12A and12B, the balloon 340 is preferably positioned distal the wire basket334. Further, the mapping electrode 354 is positioned distal the balloon340.

Prior to use, the catheter assembly 330 is positioned in the retractedposition shown in FIG. 12A. The guide wire 338 is guided to the leftatrium LA (FIG. 4B) and into a pulmonary vein PV (FIG. 4B). The catheterbody 332, including the locating device 336, are guided over the guidewire 338 to a point adjacent the pulmonary vein. The catheter body 332is then advanced such that the locating device 336 enters the pulmonaryvein PV. The mapping electrodes 354 sample electrical activity of thepulmonary vein tissue. If the mapping procedure determines that thepulmonary vein PV requires electrical isolation, the catheter assembly330 is maneuvered to the expanded position shown in FIG. 12B, wherebythe wire basket 334 expands radially. The catheter body 332 is thenadvanced axially toward the pulmonary vein such that the wire basket 334contacts the left atrium LA about the pulmonary vein ostium PVO (FIG.4B). The balloon 340 is then inflated so as to engage the pulmonary veinPV. Once inflated, the balloon 340 effectively centers the wire basket334, and thus the electrodes 352, about the pulmonary vein ostium PVO.The electrodes 352 are then energized to ablate a continuous, closedlesion pattern about the pulmonary vein ostium PVO, thereby electricallyisolating the pulmonary vein PV from the left atrium LA. If necessary,the individual wire struts 350 are cooled, such as by forcing a coolingliquid through the wire struts 350. The balloon 340 is deflated and thewire basket 334 maneuvered to the contracted position (FIG. 12A). Theentire catheter assembly 330 may then be removed from the patient.Alternatively, the catheter body 332 may be retracted from the patientalong the guide wire 338 and replaced with a separate catheter device(not shown). To this end, the catheter body 332 may be configured toprovide a rapid exchange feature, as would be apparent to one ofordinary skill.

The pulmonary vein isolation catheter of the present invention, and inparticular the substantially closed loop configuration, provides ahighly viable tool for electrically isolating a vessel, such as apulmonary vein, from a chamber, such as the left atrium. In this regard,the substantially closed loop is orientated transverse to a longitudinalaxis of the catheter assembly so as to facilitate rapid, consistentplacement of the ablation loop at a desired location along the leftatrium or other chamber wall. This transverse orientation allows forguiding of the catheter assembly in a direction parallel to the axisdefined by the vessel ostium, as opposed to a radial approach. Thus, thenumerous complications presented by prior art sliding techniques areavoided. Further, due to this transverse orientation, the catheterassembly can further be provided with a locating device extending distalthe ablation loop for easily locating a particular vessel, as well as tocenter the loop around the vessel ostium. Finally, the locating devicecan be provided with mapping electrodes such that mapping of thepulmonary vein in conjunction with ablation about the pulmonary veinostium can be achieved with a unitary device.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, the preferred embodiment hasdescribed electrical isolation of a pulmonary vein from the left atriumfor treatment of atrial fibrillation. Alternatively, the method andapparatus of the present invention may be utilized in the treatment ofother cardiac arrhythmias, such as isolating the coronary sinus from theleft atrium or isolating the outflow tract (or pulmonary valve) from theright ventricle. Further, a number of the described embodiments haveincluded a catheter body forming a single loop. Alternatively, amulti-plane coil or spiral may be formed. The coil or spiral mayincrease or decrease in diameter as it extends distally, or may have auniform diameter. Additionally, while the loop has been described aspreferably being circular, a variety of other substantially closedshapes, including square, triangular, octagonal, etc. are equallyacceptable. Also, several of the described embodiments have included alocating device for centering the loop about a pulmonary vein ostium andfor mapping a pulmonary vein. In this regard, the locating device may beconfigured to serve only as a centering device or only as a mappingdevice, or both. Finally, other features may be incorporated into thecatheter assembly. For example, to expedite deployment, the catheterassembly may be configured to slidably receive a guide wire used toposition the catheter assembly within the left atrium. Even further, thecatheter assembly may include a rapid exchange feature for quickplacement over and removal from the guide wire.

1. A catheter assembly comprising: a catheter body including a proximalportion, an intermediate portion extending from the proximal portion,the intermediate portion defining a longitudinal axis, and a distalportion extending from the intermediate portion, the distal portionforming a loop including one or more segments formed around a centralloop axis, the one or more loop segments including at least one ablationelectrode coupled thereto and the central loop axis substantiallyparallel with the longitudinal axis; a locating device including ashaft, the shaft including a distal end and a tip formed along thedistal end; and a sheath engaging the catheter body and the locatingdevice, the catheter body and the locating device slidable within thesheath between a retracted position and a deployed position; wherein,the at least one ablation electrode is adapted to create a lesion, thelesion electrically isolating a vessel from a chamber for treatment of acardiac arrhythmia; and when the distal portion of the catheter body andthe locating device are deployed, the tip of the shaft of the locatingdevice is positioned distal to the loop of the distal portion of thecatheter body and substantially parallel with the, central loop axis. 2.The assembly of claim 1, wherein the central loop axis is substantiallyaligned with the longitudinal axis.
 3. The assembly of claim 1, whereinthe central loop axis is substantially offset from the longitudinalaxis.
 4. The assembly of claim 1, wherein the tip of the shaft of thelocating device is substantially aligned with the central loop axis whenthe distal portion of the catheter body and the locating device aredeployed.
 5. The assembly of claim 1, wherein the sheath includes afirst lumen to slidably engage the catheter body and a second lumen toslidably engage the locating device.
 6. The assembly of claim 1, whereinthe sheath includes a single lumen to slideably engage both the catheterbody and the locating device.
 7. The assembly of claim 1, wherein thelocating device further includes a plurality of mapping electrodescoupled to the tip of the shaft.
 8. The assembly of claim 1, wherein thetip of the shaft of the locating device forms a coil.
 9. The assembly ofclaim 8, wherein the coil has a distally decreasing diameter.
 10. Theassembly of claim 1, wherein the tip of the shaft of the locating deviceis substantially straight when retracted within the sheath and forms acoil when deployed.
 11. The assembly of claim 10, wherein the tip of theshaft of the locating device includes a core wire.
 12. The assembly ofclaim 11, wherein the core wire is formed from stainless steel.
 13. Theassembly of claim 11, wherein the core wire is formed from a shapememory alloy.
 14. A method for forming an ablation pattern toelectrically isolate a pulmonary vein for treatment of cardiacarrhythmia, comprising: directing a tip of a locating device to locate apulmonary vein from within a left atrium, the tip extending distal of adistal portion of a catheter body, the locating device and the catheterbody slideably engaged by a sheath and the distal portion of thecatheter body forming a loop including at least one ablation electrodecoupled thereto; inserting the tip of the locating device into thepulmonary vein to center the loop of the distal portion of the catheterbody about an ostium of the pulmonary vein; and energizing the ablationelectrode to form the ablation pattern.
 15. The method of claim 14,further comprising: guiding the sheath, in which the catheter body andthe locating device are engaged in a retracted position, into the leftatrium; sliding the catheter body distally out from the sheath to deploythe loop; and sliding the locating device distally out from the sheathto position the tip of the locating device distal to the loop.
 16. Themethod of claim 14, further comprising mapping an electrical activity ofthe pulmonary vein with a plurality of mapping electrodes, the pluralityof mapping electrodes coupled to the tip of the locating device.
 17. Acatheter assembly comprising: a catheter body including a proximalportion, an intermediate portion extending from the proximal portion,the intermediate portion defining a longitudinal axis, and a distalportion extending from the intermediate portion, the distal portionforming a loop including one or more segments formed around a centralloop axis, the one or more loop segments including at least one ablationelectrode coupled thereto and the central loop axis substantiallyparallel with the longitudinal axis; a locating device including ashaft, the shaft including a distal end and a tip formed along thedistal end; and a sheath engaging the catheter body and the locatingdevice, the catheter body and the locating device slidable within thesheath between a retracted position and a deployed position; wherein,the at least one ablation electrode is adapted to create a lesion, thelesion electrically isolating a vessel from a chamber for treatment of acardiac arrhythmia; and when the distal portion of the catheter body andthe locating device are deployed, the tip of the shaft of the locatingdevice is positioned distal to the loop of the distal portion of thecatheter body, forms a coil, and is substantially aligned with thecentral loop axis.